Add UMA for studying download cancellation reasons

chrome/browser/android/download/download_manager_service.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/android/download/download_manager_service.h"
 
 #include "base/android/jni_string.h"
 #include "base/message_loop/message_loop.h"
 #include "base/time/time.h"
 #include "chrome/browser/download/download_service.h"
@@ skipping 57 matching lines @@
   if (is_history_query_complete_)
     PauseDownloadInternal(download_guid);
   else
     EnqueueDownloadAction(download_guid, PAUSE);
 }
 
 void DownloadManagerService::CancelDownload(
     JNIEnv* env,
     jobject obj,
     const JavaParamRef<jstring>& jdownload_guid,
-    bool is_off_the_record) {
+    bool is_off_the_record,
+    bool is_notification_dismissed) {
   std::string download_guid = ConvertJavaStringToUTF8(env, jdownload_guid);
+
+  content::DownloadControllerAndroid::RecordDownloadCancelReason(
+      is_notification_dismissed ?
+          content::DownloadControllerAndroid::kNotificationDismissed :
+          content::DownloadControllerAndroid::kActionButton);
   // Incognito download can only be cancelled in the same browser session, no
   // need to wait for download history.
   if (is_off_the_record) {
     CancelDownloadInternal(download_guid, true);
     return;
   }
 
   if (is_history_query_complete_)
     CancelDownloadInternal(download_guid, false);
   else
@@ skipping 115 matching lines @@
     resume_callback_for_testing_.Run(false);
 }
 
 content::DownloadManager* DownloadManagerService::GetDownloadManager(
     bool is_off_the_record) {
   Profile* profile = ProfileManager::GetActiveUserProfile();
   if (is_off_the_record)
     profile = profile->GetOffTheRecordProfile();
   return content::BrowserContext::GetDownloadManager(profile);
 }